This invention relates to uninterruptible power supply (xe2x80x9cUPSxe2x80x9d) systems, and more particularly to UPS systems used in combination with flywheel energy storage devices. The UPS""s of the present invention include one or more flywheel energy storage devices that are integrated with the UPS within a single housing. Thus, the integrated unit appears, externally, to be a single component.
UPS systems are well known. For example, one UPS system is described by Roberts U.S. Pat. No. 4,471,233, entitled xe2x80x9cEmergency Power Systemxe2x80x9d (the ""233 patentxe2x80x9d). The ""233 patent describes a motor-generator set (xe2x80x9cgensetxe2x80x9d) that is converted into a xe2x80x9ccomplete uninterruptible power supplyxe2x80x9d by adding a logic-controlled, battery-powered inverter that operates upon the failure of utility power. In such systems, a bank of chemical batteries (typically conventional automobile batteries) is connected to a battery charger that provides a trickle charge to keep the batteries energized during normal operations.
The bank of batteries then typically is located remote from the UPS electronics, at least in part, due to the various safety considerations related to the general nature of the large quantities of caustic chemicals involved. Moreover, chemical batteries, suffer from various deficiencies including bulkiness, lack of reliability, limited lifespan, high maintenance costs and relatively low safety. For example, typical large battery installations (depending on the quantity of back-up power required) often require special venting and air-conditioning systems for the dedicated battery storage rooms.
One solution for the problems related to batteries, is to provide an alternate back-up energy source, such as a flywheel energy storage unit. One example of such a UPS system is described by Gottfried U.S. Pat. No. 4,460,834, entitled xe2x80x9cUninterruptible Power Systemxe2x80x9d (the xe2x80x9c""834 Patentxe2x80x9d). The ""834 Patent describes a UPS system in which a flywheel is used to provide back-up energy to an external load in the event of a short term loss of utility power (long term back-up power, in most instances, is provided by a diesel powered genset). Systems such as that described in the ""834 patent typically include a controller unit, a long term back-up power unit, and a short term back-up power unit. The controller often includes transfer switches, control electronics, and input/output lines that interconnect utility power, short term back-up power, and long term back-up power to the load. The short term power unit may include a motor, a generator and a flywheel unit (see, e.g., column 4, lines 51-60).
Common problems with existing systems, regardless of whether they utilize a flywheel or batteries for short term back-up power, include large floor-space requirements, excessive cooling requirements, reduced reliability, and high cost due, at least in part, to multiple electronic control systems. Additionally, UPS systems that rely on batteries for short term back-up power also suffer from increased safety problems related to the caustic nature of the battery acid, such as additional venting requirements.
In view of the foregoing, it is an object of this invention to provide improved UPS systems that efficiently provide short term back-up power to a load.
It also is an object of this invention to provide improved UPS systems that have reduced cooling requirements.
It further is an object of this invention to provide improved UPS systems that have a reduced xe2x80x9cfootprint,xe2x80x9d in that they take up less floor space than conventional UPS systems.
A still further object of this invention is to provide methods and apparatus for reducing the manufacturing costs related to UPS systems.
These and other objects of the invention are accomplished in accordance with the principles of the invention by providing integrated flywheel UPS systems that are contained in a single physical unit. The preferred embodiments include a compact flywheel energy storage unit that is mounted to a chassis that also contains UPS controller electronics. The two otherwise independent systems are configured such that a single cooling system may be employed to cool the integrated unit. Moreover, locating the otherwise independent systems in a single housing enables the system designers to utilize, for example, shared: control electronics, displays, user interface systems, fusing, DC bus capacitors, and other provisions, such as a shared emergency shut-off system. Additional advantages occur because certain interconnecting components are eliminated in their entirety. The single housing unit is substantially smaller than the combination of the two individual units, and thus has a smaller footprint than conventional systems.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.